Conventionally, as disclosed in U.S. Pat. No. 5,754,965, a technique for diagnosing and analyzing vehicle behaviors based on detection signals of various sensors installed in a vehicle is well known. Further, a technique to memorize, as vehicle travel information, output information of various sensors at a time of collision or the like, before and after an impact is also known.
Further, in a conventional diagnosis scheme a diagnostic code is stored at a time of sensor/actuator abnormality. In addition, time-lapse sensor outputs and time-lapse control data outputs is stored as the vehicle travel information (i.e., freeze frame data).
However, the diagnostic code and the freeze frame data are stored only at a time of sensor/actuator abnormality in the conventional diagnosis scheme. Therefore, such scheme does not enable the storage of the vehicle travel information at a time of, for example, a non-corresponding vehicle behavior that does not correspond to a driver's driving operation while no sensor/actuator abnormality is observed. As a result, even when the non-corresponding vehicle behavior is being generated, a cause of such vehicle behavior may not be analyzed based on the vehicle travel information in the conventional diagnosis scheme.